A pandemic is a worldwide outbreak of a disease that affects or kills large numbers of people over a broad geographic area and across countries and continents. It differs from an epidemic, which occurs only in a small number of cases and usually does not spread easily between communities.
In humans, pandemics typically start when a virus that normally only occurs in animals (e.g., bats, birds, rodents) jumps from animals into human populations. This is what happened with the Black Death that caused mass deaths in Europe in the 14th and 17th centuries. It was transmitted by fleas that hitched a ride on shipboard rats. More recently, a cholera pandemic began in 1961 for the first time outside of India’s Ganges River delta region and ravaged parts of Asia. It also occurred in the 1970s in South America and continued into the 1990s.
The 1918 Spanish flu pandemic was the worst of its kind. A combination of close quarters in the crowded cities and the massive movement of troops during World War I helped it spread. It is estimated that it killed up to fifty million people.
During a pandemic, you can help protect yourself and your family by following simple health advice. Wash your hands often and cover coughs or sneezes. Avoid crowds, and stay 1.5m apart from people. If you must be in a crowded place, wear masks (unless you are at a hospital or other health service). Avoid shaking hands and hugging. Stay home if you are unwell. If you have children, make sure they receive their immunisations. In some states and territories, health authorities may impose restrictions, such as cancelling public events or closing schools.